Installing batteries with solar is necessary on off-grid systems if you want power at night and also becoming more popular on grid-tied systems. Choosing what type of batteries to install can be a bit complicated so this article will cover the basics for you.
The batteries that are most commonly used for solar are lead acid and lithium chemistries. No matter what, you will want to choose a “deep cycle” battery that is rated in amp hours (AH) and not a starting battery that is rated in cold-cranking amps (CCA). Car batteries are great for providing a lot of amps really fast to start a motor but they don’t do well with the long, slow draw of running the lights, TV and refrigerator in your home or off-grid cabin. If it is the zombie apocalypse and car batteries are all you can find, they will work but they aren’t the best choice for the application.
Let’s start with lead acid batteries which can be broken down into the two basic types of flooded and sealed. Flooded batteries will be less expensive but they require maintenance and ventilation. When you purchase flooded batteries you are committing to adding distilled water to the batteries on a monthly basis. Without the added water, they can run dry which means they lose all charge and are likely to never hold a charge again. If you are not good at regular maintenance, buying these batteries can be a costly mistake. Even if you get the self-watering kit that does the work for you, you still need to maintain water in the reservoir and check to make sure the kit is correctly maintaining the water levels high enough. The ventilation requirements are also very important to consider because these batteries will vent hydrogen gas which is poisonous and flammable. Installing these batteries in your living space or anywhere there might be an open flame could have some nasty results.
Sealed lead acid batteries are a little pricier but solve the unpleasant issues of the flooded batteries. You do not have to add water to them, they do not vent large amounts of poisonous, flammable gas and they can also be installed on their sides without worries about hazardous chemical leakage. The most available types of sealed batteries are gel and AGM. These are also often referred to as VRLA for Valve regulated lead acid batteries.
Even within the categories of sealed and flooded lead acid batteries, there are different technologies being employed. For example, the Outback EnergyCell Non-Carbon batteries are a type of enhanced sealed lead acid batteries that have improved charging efficiency and a better cycle life in applications where they are regularly at a partial state of charge which means they last longer in off-grid and self-consumption applications.
Lithium batteries are enjoying increased popularity in the last few years as they have come down in price and are more available than ever before. There are different Lithium chemistries available but more importantly, the lithium batteries can be very different voltages. There are 2 volt, 6 volt and 12 volt Lithium batteries which match the voltages you see with typical lead acid batteries. These Lithium batteries also tend to look a lot like their lead acid counterparts and will either sit on the floor or a battery rack or cabinet. Other Lithium batteries like the LG Chem RESU are around 300 volts and hang on the wall for a sleek look. When choosing a Lithium battery system it is important to make sure you are getting an inverter that is compatible with the voltage of the battery. Some inverters, like the Outback Radian, are designed to run with a 48 volt battery bank while inverters like the SolarEdge StorEdge are set up to work with the 300 volt battery.
When comparing lithium to lead acid, the lithium batteries will usually be more expensive but are designed to last longer. Also, if you are comparing the amount of storage it is important to note that lead acid batteries can generally only be discharged to 50% of their capacity while Lithium batteries can usually go all the way down to 10% capacity. This means if you are looking at batteries with the same storage capacity, you will get a lot more usable energy from the Lithium battery over the lead acid battery.
So now you are an informed battery purchaser. If you were using your confusion about battery types as a reason to procrastinate on purchasing your system, you will have to come up with a different excuse, or better yet, go ahead an buy the system that is right for you. Call (866) 798-4435 for more information.